Process for the manufacture of manganese or of manganese alloys poor in carbon and silicon



Patented Jan. 8, 1924.

UNITED STATES PATENT OFFICE.

no MICHAEL STURE KALLING AND SVEN DAGOBERT DANIELI, OF TROLLHATTAN,

SWEDEN, ASSIGNOBS TO AKTIEBOLAGET FEB-BOLEGEBINGAR, OF STOCKHOLM,SWEDEN, A LIMITED JOINT STOCK COMPANY.

PROOESS FOR THE MANUFACTURE OF MANGANESE OR OF MANGANESE ALLOYS POOR INCARBON AND SILICON.

No Drawing,

To all whom it may concern:

Be it known that we, Bo MICHAEL S'rURE KALLING and Swan DAGOBERTDANIELI, subjects of the King of Sweden, residing at Trollhattan, in theKingdom of Sweden, have invented new and useful Improvements inProcesses for the Manufacture of Manganese or of Manganese Alloys Poorin Carbon and Silicon, of which the following is a specification.

The present invention relates to a process for the manufacture ofmanganese, or manganese alloys, poor in carbon and silicon, especiallythose with low percentages of phosphorus and iron, from manganese ores,whose principal content of manganese occurs in the form of oxides ofmanganese, in which the average degree of oxidation of the manganese ishigher than is represented by the formula MnO, such for example asmanganese ores which contain one or more of the minerals braunite,hausmannite, pyrolusite, polianite, psilomelan, or the like.

It is well known that manganese, or manganese alloys poor in carbon, canbe manufactured in the following manner. Substances containing oxides ofmanganese, may be smelted with, or while in a molten condition broughtinto contact with silicon, or with alloys which containsilicon--preferably those containing more than 10% Si, as not until thispercentage of silicon has been reached will the content of carbon havedecreased sufficiently to be regarded as low, for exampleferro-silicon,ferro-silicomanganese, ferrosilico-aluminium-manganese,etc.

In order that this method may be usable for the manufacture of manganesealloys, it is indispensable that the reduction with silicon should takeplace under such conditions that neither the reagents nor the productsformed by the reaction shall be capable of absorbing any appreciablequantity of carbon. For obtaining this result one may for instance usean electric furnace, the lining of which does not contain any carbon andin which the heat generation takes place in a free electric are or arcsformed between two or several points of electrodes which are not incontact with the charge (for instance a furnace of the so calledRennerfelt-type). The chemical reactions which may take Applicationfiled February 1, 1922. Serial No. 533,382.

place in the process in question may be expressed schematically by thefollowing formula:

The reaction does not proceed quantitatively, but ceases when therelation between the content of manganous oxide in the sili cate slagformed, on the one hand, and the content of silicon in the manganesealloy formed, on the other hand, has reached a certain value, whichvalue is a function of the content of silicon in the manganese alloyformed, and which relation increases accord ing as the content ofsilicon in the alloy decreases.

In order that the content of silicon in the alloy obtained shall be low,it is essential that the content of manganous oxide in the silicate slagsimultaneously formed, shall be high. Hence it is obvious that theconsumption of silicon per unit of weight of reduced manganese will behigher, according as the degree of oxidation of manganese oxide to bereduced increases.

In order that the process of reduction in question maybe carried outwith the smallest possible consumption of silicon, and thus with thegreatest possible economy, it is desirable that the degree of oxidationin the manganese of the manganese ore used shall be lowered as far aspossible before the reduction with silicon is started.

It is conceivable that, inasmuch as it is well known that manganeseoxides of a higher average degree of oxidation than MnO can be reducedto MnO with carbon monoxide or other reducing gases, a preparatoryreduction of the ore with such gases might be practicable, However, inview of the practical difliculties of carryin out such a process on alarge scale, this soIution can scarcely be of any but academic interest.

In accordance with the present invention, the problem is solved in thefollowing manner :Manganese ore, whose content of manganese consistsprincipally of man anese oxides with an average degree of oxidationabove Mn(), is smelted with a quantity of reducin carbon sufficient tobind the oxygen which t e manganese oxides of the ore contain beyond thedegree of oxidation MnO.

preciable This reducing carbon is in addition to the quantity ofreducing carbon that may be combusted with the carbon dioxide and waterwhich may be given off by the ore during the smelting, and whichquantity must be ascertained by experimental tests in each individualcase. It has in fact been definitely ascertained, that no appreciablereduction of metallic manganese takes place until practically all themanganese in the ore has been reduced to the degree of oxidation whichcorresponds to the formula MnO.

It is obvious that by the present process a manganese ore admirablyadapted for reduction with silicon will be obtained.

As a rule, manganese ores of the kind in question usually contain largeror smaller quantities of metal oxides, which are more easily reduciblewith carbon than is MnO, for example oxides of iron. In case it isdesired that the alloy poor in carbon and silicon shall have the lowestpossible content of metals whose oxides are more easily reducible thanMnO, it is advisable to increase the quantity of reducing carbonsupplied in the smelting process, so that the bulk of the said metaloxides shall be re duced to metal. Curiously enough, no apuantity ofmanganesewill follow along in tie'reduction.

Certain manganese ores of the kind in question, though otherwise good,contain appreciable quantities of phosphorus. When such ores are reducedwith carbon to metal, practically the entire phosphorus content of theore is obtained in the metal.

If it is desired that the manganese alloy poor in carbon and siliconshall be as far as possible free from phosphorus, it 18 possiblc. byequivalent increase of the admixture of carbon in the preparatorytreatment of the ore with reducing carbon in accordance with the presentprocess (in spite of the fact that phosphorus-pent oxide is moredifiicult to reduce than MnO) to have the phos horus practicallvspeaking. totallv reduced. without entailing the reduction of amappreciable quantities of manganese. provided only that iron insufficient quantities to bind the phosphorus so reduced is sinnltaneouslv reduced. Should the mannesc ore which, in accordance withthe present process. is to be treated with reducing carbon. contain toolow a percentage of iron in proportion to that of phosphorus, it isadvisable. in smelting the manganese ore with reducing carbon, to add asuitable quantity of oxides of iron, for example iron ore. w

it i also evident from the above that manganese ores which. owing to toohigh a percentage of iron or too high a perccntaqe of phosphorus. orboth. are otherwi e not adapted for the manufacture of manganese alloys,may be converted by the present containing manganese oxides (themanganese ores) should be supplied on the surface of a inolten bath ofsilicon heated to a suitable temperature, for example in the form ofsilico-manganese or high-per cent ferrosilicon. In that case, however,the reaction between the silicon ofthe alloy rich in silicon and theoxides of manganese ore can take place only in the surface of contactbetween the .alloy rich in silicon and the i manganese ore, andtherefore the reaction must proceed comparatively slowly, and its speedwill necessarily be lowered according as the concentration of silicon inthe alloy, or the concentration of manganese in the ore, is lowered. Inaccordance with the present invention, the mixing of the reagents iseffected in the following manner: silicon, for example in the form ofsilico-manganese or high per cent ferro-silicon, is successivelysupplied in finely divided form on the surface of a molten bath of theore previously treated with reducing carbon.

Ever little grain of the silicon, or the alloy rich in silicon, is thusconverted (as soon as the reaction between the silicon and the manganousoxide commences) into a little drop of silico-manganese alloy, thespecific weight of which increases owing to i the {Qiringmfl' of siliconand the absorption of manganese. so that it becomes heavier than themolten manganese ore, and sinks dow'n through the latter. The surface ofcontact between the drops of silico-manganese and the molten manganeseore is, of course, comparatively large, and, if the concentrationpfmanganous oxide in the molten ore is sufficiently high, and the pathwhich the drop of silico-manganese has to traverse in its downwardprogress through the ore is sufiiciently long. practically all thesilicon will have been oxidized during the fall of the drop. so that.manganese. or a manganese allov poor in carbon and silicon will collectunder the cover of molten manganese ore. This result. however. issubiect to the condition that neither the reacting substances nor thereaction products are allowed durinc the process to absorb appreciableouantifies of carbon.

Owin'r to the reaction of the motel drops with the molten manganese ore.the latter will be continuou ly deprived of manoanous oxide and enrichedwith silicon dioxid. so that the concentration of manganous oxidetherein will eventually approach the limit when silicon is no longeroxidized to a satisfactory extent. The su ply of silicon must then bediscontinued and the furnace emptied, whereu on-a new bath of manganeseore previous y reduced by smelting with carbon should be prepared, andthe supply of silicon can be recommenced.

As experience has shown that the molten manganese bath need not be verydeep, the process can also be performed in the following manner. To ashallow manganese bath (which as a rule remains in the furnace when itis tapped off) is supplied a mixture of unmelted, previously reducedmanganese ore, preferably in a finely pulverized state, and finelypulverized silicon, for example in the form of an alloy, a mixture soadjusted that the Mn() concentration of the ore bath, owing to thesuccessive supply of MnO entailed by the melting of the charge, and inspite of the successive absorption of silicon dioxide and reduction ofmanganese, is kept constant, until the furnace chamber is filled andmust be emptied. This latter form of the process has the advantage thatit is easier to protect the silicon of the alloy supplied againstoxidation with free oxygen, and to prevent the Caking of the smallgrains of the silicon alloy used for the reduction.

The actual performance of the process can, of course, be carried out inany furnace of suitable construction, but the process may mostconveniently be performed in electric furnaces of a suitable type, andin one of the following ways: Either by using a sin gle furnace in whicha suitable qmmtity of manganese ore is first preparatorily reduced withcarbon, whereupon the silicon is supplied on the surface of the bath ofmolten ore thus obtained, or else by preparatorily reducing themanganese ore with carbon in onefurnace, and thereu on eitherdischarging it in a molten condition direct into another furnace, inorder there to be treated with silicon, or moulding it, after discharge,in suitable receptacles, where it is allowed ts harden, in order to betransferred in a solid state-if desired, after grinding-to the secondfurnace, where the treatment with silicon is to take place.

Athird combination, in which the same furnace is used alternately forthe production of previ'ously reduced manganese ore, which, afterdischarge, is allowed to harden, and for the reduction, with the aid ofsilicon, of preparatorily reduced ore, obviously coincides in principlewith the latter of the above-mentioned alternatives.

It is obvious that, whichever alternative is selected, the lining of thefurnace in which the reduction with silicon takes place, must notcontain any appreciable quantity of carbon.

In the reaction between the preparatorily reduced manganese ore and thesilicon, there is obtained, as above mentioned, a silicate slag whichcontains manganous oxide, and whose manganese content must be kepthigher according as the silicon content in the manganese alloy poor incarbon is lower. It has, however, been found possible within certainlimits to diminish the manganese content in this slag, provided the slagcontains other bases. For example, it has been ascertained that twoslags, one of which contained MnO and 30% SK), and the other 35% MnO and30% Ca() as well as 35% Si(),, were in this respect equivalent.

The importance of this discovery lies principally in the fact that, perunit of weight of silicon consumed in the reduction, a smaller quantityof manganese in the form of slag, when lime (or other bases) is suppliedto the process during the reduction with silicon is obtained, than whensuch bases are not supplied.

in the special case wherc a silico-manganese alloy is used as a reducingagent, it is possible to contrive that the slag precipitated as abyproduct shall not contain a larger quantity of manganese than can beentirely utilized for the manufacture of the quantity ofsilico-mangancse with which lho reduction of the preparatorily reducedinangancsc ore is effected. In the production of silico-nuingauese alloyfrom such slag, one can as a rule count on an output of manganese of notless than 99%. This entails the advantage that the present process canbe employed without the precipitation, as a by-product. of slug whichrequires to be used for the numufacture "of other mangrancse alloys.

l reduction with silicon (where lime has been added in the process) ofthe preparatorily reduced manganese ore, it has been found that if thelime has been insuf' iicicntly burned, or, if after the burning it hasbeen allowed to lie for some time before use, part of the siliconsupplied will be oxidized by oxidizing gases present in the lime, suchas carbon dioxide and water.

it has been found possible to obviate this drawback by supplying lime(or other bases) to the manganese orc simultaneously with the smeltingof the latter with carbon. it has in fact been found, curiously enough,that a slag which in the aggregate consists of MnO and (laO as to over90%, is comparatively easily smelted, while at the same time it does not(in contra-distinction from high-basic calcium silicate slugs) crumbleinto powder if kept for some length of time.

The fusibility is further increased by the presence of silicon dioxide,the content of which, however, need in no case exceed 15%. The fact thatit has been possible to supply bases already in the first stage of theprocess also entails the advantage that limestone,

and silicon, (A) with the use of the process which is the subject of thepresent invention, and (B) with previously known processes.

For the sake of completeness, the formulae for the reactions which takeplace when the silicate slag, rich in manganous oxide, obtainedas aby-product, is worked up into ferro-slhco-manganese, are also appended.

A. Manufacture of ferro-manganese poor in carbon and silicon inaccordance with the 7 process which is the subject of the presentinvention:

1. Preparatory reduction of the manganese ore with carbon.

(manganese ore with circa 6ll% Mn, (quartz) (burnt Fe and 5.5% SiCn)lime) 2. The reduction with silicon in the form of ferro-sihco-manganeseof the manganese geducg carbon) 47M110.16CaO.FeO.6SiO, Fe MnC CO(preparatorily reduced Mn ore with (Spiegel iron (escaping MnO and 1.2%Fe) wit l 23% Mn) gases) ore preparatorily reduced with carbon with theaddition of lime.

sumo-manganese alloy with 25% Si, M11, 0.8% c

3. The conversion of the silicate slag nese alloy.

(preparetorlly reduced manganese ore) (silicate slag with 33% Mn)(ferro-mnnsanese with 94% Mn 1% Si and 0.5% i.

22MnO.16CaO. i sio 4Si0, FeO 500 2MnO.16Ca0.9SiO Si Mn FeC 4900(reducing carbon) iron be10nging to ducing carbon) B. Manufacture ofterm-manganese poor in carbon and 51110011 in accordance w1th previousknown processes:

(silicoqnnnaanese alloy with 2 Si, 70% Mn and 0.8 carbon) (Mn-ore withcirca 60% Mn, 5% Fe, 5.5%

2. Conversion of the silicate slag richin silico-manganese alloy:

(waste slag with 7% Mn.) (escaping Reduction of the manganese ore withsilicon in the form of a silico-manganese alloy.

.20 (silicate slag with 55% Mn) (ferro-rnanganese wit circa 83% Mn, 0.8%C

and 1% Si) manganese, obtained as a by-product, into sa enn sio14.07Si(),+ asses 57.66

(silicate slag with (quartz) (oxide of iron (reducing 55% Mn)accompanycarbon;

ing quartz and reducing carbon) 1.8a +0.92)Si ,Mn,,.Fe.C+ 154.7900+5.72Mn +5.69%.

(lerro-silico-manganeso) On comparing the above formulae it will hefound that:

(a) 1n the present process about 52% of the manganese content of the oresupplied to the process is recovered in the manganese alloy poor incarbon. while in the previous process merely somewhat over10% isobtained in the reduction with silicon.

(1)) Per unit of weight of manganese ob tained in the form of amanganese alloy poor in carbon, the consumption of reducing silicon isabout 90% higher in the latter than in the former case.

(c) The consumption of ore per unit of (escaping gases) weight ofmanganese obtained in the form of manganese alloy poor in carbon. is inthe latter case about 44% higher than in the former.

(d) The manganese content in the alloy poor in carbon obtained is about10% higher in the former than in the latter case.

(6) The content of carbon in the former case is scarcely more than halfas large as in the latter.

(f) In the latter case the silicate siag rich in manganese, obtained asa byproduct, contains so large a' quantity of manganese that it cannotbe fully utilized for the manufacture of the equivalent quantity ofsilicomanganese alloy with which the reduction took place, whence itfollows that, when the earlier process is adopted, the manufacture, inorder to yield the best possible economic results, must be combined withthe manufacture of, for example, ordinary ferro-manganese rich incarbon, or silico-manganese alloys. It should be observed that amanufacturing process which in order to pay, has to be combined withanother kind of manufacture, as a rule, diminishes the value of theprocess.

It is to he understood that Wherever we have used the expressionmanganese in the specification and claims, this expression is intendedto cover not only manganese as such, but also alloys thereof, and wherewe have used the expression manganese alloy it is intended to cover notonly an alloy of manganese, but manganese as metal.

Having thus described our invention we declare that what we claim is:

1. The process of manufacturing manganese poor in carbon and silicon,and having low percentages of phosphorus and iron. which consists insmelting manganese ores in which the principal content of manganeseoccurs in the form of manganese oxides having an average degree ofoxidation of the manganese higher than is represented by the formula MnOin an electric furnace with a quantity of reduction-carbon adapted toreduce the main part of the higher manganese oxides of the ore intomanganous oxide a part of the eventually occurring iron oxides to ironand apart of the eventually occurring phosphoric combinations tophosphorus then reducing the prereduced manganese ore in an electricfurnace by silicon in the form of alloys preferably having more than 10%of silicon, the latter reduction taking place under such conditions thatthe metal formed has no opportunity to absorb any appreciable quantityof carbon.

2. The process of manufacturing manganese poor in carbon and silicon,and having low percentages of phosphorus and iron,

which consists in smelting manganese ores in which the principal contentof manganese occurs in the form of manganese oxides having an averagedegree of oxidation of the manganese higher than is represented by theformula MnO in an electric furnace with a quantity of reduction-carbonadapted to reduce the main part of the higher manganese oxides of theore into manganous oxide a part of the eventually occurring iron oxi esto iron and a part of the eventually'occurring phosphoric combinationsto phosphorus, then reducing the prereduced manganese ore in an electricfurnace by silicon in the form of alloys preferably having more than 10%of silicon, said silicon being supplied in a finely pulverized state onthe surface of a molten bath of prereduced manganese ore, the latterreduction taking place under such conditions that the metal formed hasno opportunity to absorb any appreciable quantity of carbon.

3. The process of manufacturing manganese poor in carbon and silicon.and having low percentages of phosphorus and iron, which consists insmelting manganese ores in which the principal content of manga neseoccurs in the form of manganese oxides having an average degree ofoxidation of the manganese higher than is represented by the formula MnOin an electric furnace with a .quantity of reduction-carbon adapted toreduce the main part of the higher manganese oxides of the ore intomanganous oxide, a part of the eventually occurring iron oxides to ironand a part of the eventually occurring phosphoric combinations tophosphorus, then reducing the prercduccd manganese ore in an electricfurnace by silicon in the form of alloys preferahl hav iug more than10); of silicon, the silicon being supplied in a finely pulverized stateand mixed with pulverized prerednced manganese ore on the surface of amolten bath of prereduced manganese ore. the latter re duction takingplace under such conditions that the metal formed has no opportunity toabsorb any appreciable quantity of carbon 4:. The process ofmanufzu'turing manganese poor in carbon and silicon, and having lowpercentages of phosphorus and iron,'

which consists in smelting manganese ores in which the principal contentof manganese occurs in the form of manganese oxides having an averagedegree of oxidation of the manganese higher than is represented by theformula llInO in an electric furnace with a quantity of reduction-carbonadapted to reduce the main part of the higher manganese oxides of theore into manganous oxide, a part of the eventually occurring iron oxidesto iron and a part of the eventually occurring phosphoric comhi nationsto phosphorus, then reducing the prereduced manganese ore in an electricfurnace by silicon in the form of alloys preferably having more than 10%of silicon, said silicon being supplied in a finely pulverized state andmixed with ulverized prereduced manganese ore and asic substances suchas lime on the surface of a molten bath of prereduced manganese ore, thelatter reduction taking place under such conditions that the metalformed has no opportunity to absorb any appreciable quantity of carbon.

5. The process of manufacturing man anese poor in carbon and silicon,and havmg low percentages of phosphorus and iron, which consists insmelting manganese ores in which the princi al content of manganeseoccurs in the orm of manganese oxides having an average degree ofoxidation of the manganese higher than is represented by the formulaM110 in an electric furnace together with lime and a quantity ofrcductioncarbon adapted to reduce the main part of the higher manganeseoxides of the ore into manganous oxide, a part of the eventuallyoccurring iron oxides to iron and a part of the eventually occurringphosphoric combinations to phosphorus, then reducing the prereducedmanganese ore in an electric furnace by silicon in the form of alloys,prc ferably having more than 10% of silicon, the latter reduction takingplace under such conditions that the metal formed has no opportunity toabsorb any appreciable quantity of carbon.

6. The process of manufacturing manganese poor in carbon and silicon,and having low percentages of phosphorus and iron,

which consists in smelting manganese ores in which the principal contentof manganese occurs in the form of manganese oxides having an averagedegree of oxidation of man ganese higher than is represented by theformula MnO in an electric furnace together with lime and a quantity ofreduction-car: bon adapted to reduce the main part of the highermanganese oxides of the ore into manganous oxide. a part of theeventually occurring iron oxides to iron and a part of the eventuallyoccurring phosphoric combinations to phosphorus, then reducing theprereduced manganese ore in an electric furnace by silicon in the formof alloys preferably having more than 10% of silicon, said silicon beingsupplied in a finely pul; verized state on the surface of a molten bathof prereduced manganese ore, the latter reduction taking place undersuch conditions that the metal formed has no opportunity to absorb anyappreciable quantity of carbon.

e process of manufacturing manganese poor in carbon and silicon, andhaving low percentages of phosphorus and iron, which consists insmelting manganese ores in which the principal content of manganeseoccurs in the form of manganese oxides having an average degree ofoxidation of the manganese higher than is re resented by the formulaMini) in an electric urnace together with lime and a quantity ofreduction'carbon adapted to reduce the main part of the higher manganeseoxides of the ore into manganous oxide, a part of the eventuallyoccurring iron oxidcs to iron and a part. of the eventually occurringphosphoric combinations to phosphorus, then reducing the prereducedmanganese ore in an electric furnace by silicon in the form of alloyspreferably having more than 10% of silicon, said silicon being suppliedon the surface of the molten bath of prereduced manganese ore in afinely pulverized state and mixed with pulverized manganese ore, thelatter reduction taking place under such conditions that the metalformed has no opportunity to absorb any appreciable quantity of carbon.

8. The process of manufacturing manganese poor in carbon and silicon,and having low percentages of phosphorus and iron, which consists insmelting manganese ores in which the principal content of manganeseoccurs in the form of manganese oxides having an average degree ofoxidation of the manganese higher than is represented by the formulaMnOin an electric furnace togetherwvith lime and a quantity ofreduction-carbon adapted to reduce the main part of the higher manganeseoxides of the ore into manganous oxide, a part of the eventuallyoccurring iron oxides to iron and a part of the eventually occurringphosphoric combinations to phosphorus, then reducing the prereducedmanganese ore in an electric furnace by silicon in the form of alloyspreterably having more than 10% of silicon, said silicon being suppliedin a finely pulverized state and mixed with pulverized prereducedmanganese ore and basic substances such as lime, on the surface of themolten bath of prereduced manganese ore, the latter reduction takingplace under such conditions that the metal formed has no opportunity toabsorb any appreciable quantity oi carbon.

In testimony whereof We have signed our names to this specification.

B0 MlCllllllL STURE KAhhlNG. SVEN DAGOBEB/l llANIEhl. W'itnesses v AUG.HAGELIN, E. NILON.

